External causes of death after severe traumatic brain injury in a multicentre inception cohort: clinical description and risk factors.

Objective: To characterize the clinical profile of patients dying from external causes (EC) following severe traumatic brain injury (TBI). Design and Methods: Data from 2545 patients forming the NSW-BIRP inception cohort discharged from post-acute inpatient rehabilitation between 1 July 1990 and 1 October 2007 were retrospectively reviewed. Standardized mortality ratios (SMRs) were calculated for EC sub-categories. Demographic, clinical and rehabilitation service factors were compared between deaths from EC, deaths from other causes (OC), and non-deceased. Clinical profiles of EC sub-categories were analysed descriptively. Results: Overall, patients with TBI were 5.2x more likely to die from EC relative to the general population. Risk of death was elevated in all EC sub-categories examined, with the largest risks relating to other accidental threats to breathing (SMR = 33.0; 95%CI = 13.79-60.45) and falls (SMR = 14.3; 95%CI = 5.01-28.39). The EC group were younger, more likely to have pre-injury psychiatric histories, less severe injuries, greater functional independence, and die earlier than the OC group. There was considerable heterogeneity in the clinical profiles of patients dying from different EC sub-categories. Conclusions: EC constitutes one of the largest causes of mortality following TBI in patients surviving beyond the post-acute phase. Potential implications for risk modification and prevention of premature and avoidable deaths are discussed.